1. Field of The Invention
The present invention relates to the field of local area networks (LANs) using the Ethernet communication protocol (e.g., the IEEE 802.3 Standard). Specifically, the present invention relates to a probe design for monitoring information transmitted over a point to point communication link of a fast Ethernet LAN.
2. Related Art
Networked communication systems ("networks") are very popular mechanisms for allowing multiple computer and peripheral systems to communicate with each other. Local area networks (LANs) are one type of networked communication system and one type of LAN is the Ethernet communication standard (IEEE 802.3). One Ethernet LAN standard, 10 BaseT, communicates at a rate of 10 Megabits per second while another Ethernet LAN standard, 100 BaseT, communicates at a rate of 100 Megabits per second.
There are many well known reasons for which the traffic over a LAN is monitored and monitoring typically uses probes and monitoring equipment. FIG. 1A illustrates a prior art Ethernet LAN system 10 using the 10 BaseT communication standard in which traffic is monitored. In system 10, several communication nodes (e.g., computer systems) 12-18 are individually coupled through communication links to ports of a repeater hub ("repeater") 20. The repeater hub 20 repeats every communication it receives from a node to all other nodes that are coupled to the ports of the repeater 20. Therefore, in order to monitor the traffic of the entire system 10, a single probe 22 can be coupled to a port of the repeater 20 and it then receives all messages that are broadcast by any node 12-18. Although the monitoring configuration of system 10 is relatively straight forward, its communication speed is relatively slow because the technology requires that all messages from one node be repeated (e.g., re-transmitted) by the repeater 20 to all communication nodes in system 10 thereby reducing the overall bandwidth of system 10.
FIG. 1B illustrates a point to point communication link 40 within a fast Ethernet LAN system that allows much faster communication rates compared to the 10 BaseT system 10 of FIG. 1A. In fast Ethernet, e.g., of the 100 BaseT, 100 BaseT2, 100 BaseTX, or 1000BaseT communication standards, repeater hubs are replaced by equipment (e.g., switches, managed hubs, etc.) that establishes point to point communication links 46 between two communication nodes 42 and 44. In this framework, a message sent from one node to the switched hub is not automatically repeated to all other nodes coupled to the switched hub, but is rather communicated only to a select number of other nodes, or, only communicated to a single other node, as shown in FIG. 1B. In the system of FIG. 1B, it is not uncommon for one communication node 42 to have its own bi-directional communication link 46 with another communication node 44. In fast Ethernet LAN systems, the only way to monitor the traffic over the system is to monitor the communication traffic over individual communication links 46 that the system forms between the various communication nodes of the LAN.
As shown in FIG. 1C, within fast Ethernet LAN systems, probe equipment 52 is inserted between prior art communication link 46. This causes the communication link 46 (FIG. 1B) to be separated into two links 46a and 46b that individually link the probe 52 to node 42 and the probe 52 to node 44, respectively. Once inserted between the communication link 46, the probe 52 can gather any required traffic information with respect to the communication link between nodes 42 and 44. However, probe 52 electrically interrupts the communication link 46 because it is inserted in series with the nodes 42 and 44.
There are several disadvantages to the probe configuration shown in FIG. 1C. The first disadvantage is that power down and power interruption protection circuitry must be placed within the probe equipment 52 because if a power interruption occurs, communication between links 46a and 46b will become broken. This power down and power interruption protection circuitry typically includes one or more relays that are used to bypass the monitoring circuitry within probe 52 if power should be interrupted or removed from the probe 52. The relay circuit within probe 52 then restores the communication link 46 during periods of power interruption. However, this circuitry is very expensive and adds to the overall cost of the probe equipment 52. Further, the power interruption prevention circuitry does not switch immediately after the power failure, but rather requires some latency period to restore the communication link 46. During this latency period, the communication link 46 is broken which can cause data loss and/or initiate an auto-negotiation session between node 42 and node 44. Both of these factors further delay communication over point to point communication link 46. It would be advantageous to provide a probe that eliminates the need for power down and power interruption protection circuitry.
The second disadvantage to the probe equipment configuration of FIG. 1C is that the probe 52 must act as a repeater in repeating messages received from node 42 for node 44 and in repeating messages received from node 44 for node 42 because the probe 52 is inserted in series between node 44 and node 42. The act of repeating these messages introduces unwanted latency in the communication between nodes 42 and 44. It would be advantageous to provide a probe that eliminates the need to repeat messages between the linked nodes of a point to point communication link.
The third disadvantage to the probe equipment configuration of FIG. 1C originates due to auto-negotiation sessions between node 42 and node 44. When probe equipment 52 is first placed between communication link 46, the link 46a auto-negotiates between probe 52 and the node 42. Simultaneously, link 46b auto-negotiates between probe 52 and the node 44. Each auto-negotiation session is independent and can, unfortunately, result in an auto-negotiated speed of 10 Megabits for one node (e.g., node 42) and 100 Megabits for the other node (e.g., node 44). This is an impermissible result as the probe equipment 52 is not configured to allow split rate communication between its two different ends. Therefore, specialized software is included within the circuitry of probe 52 to: (1) detect when split rate communication is auto-negotiated; and (2) force the higher communication rate down to 10 Megabits. This specialized software is expensive and adds to the overall cost of the probe 52. Further, the auto-negotiation sessions initiated by an inserted probe 52 and the specialized software (1) takes time to determine if split rate communication was auto-negotiated and also (2) takes time to alter the communication rate of one of the links (e.g., link 46b). Each of the above further introduces unwanted latency in the communication between nodes 42 and 44. It would be advantageous to provide a probe that eliminates the need to auto-negotiate with each communication node of a monitored point to point communication link.
Accordingly, the present invention provides effective probe and monitoring equipment that can be used for monitoring traffic over a point to point communication link but eliminates the need for power down and power interruption protection circuitry. The present invention further provides a probe and monitoring equipment that can be used for monitoring traffic over a point to point communication link but eliminates the need to repeat messages between the linked nodes. Also, the present invention provides a probe and monitoring equipment that can be used for monitoring traffic over a point to point communication link but eliminates the need to auto-negotiate with each communication node of a monitored communication link. These and other advantages of the present invention not specifically mentioned above will become clear within discussions of the present invention presented herein.